The present invention pertains generally to a machine for preparing a planographic subtractive plate, such as a lithographic plate, for printing, and pertains more particularly to an improved processing machine in which a plate to be developed is passed by means of rollers through a developing station in which it is treated with developer.
Machines of this type are known, for example from U.S. Pat. No. 3,732,808, issued May 15, 1973, to Robert C. Graham for an APPARATUS FOR DEVELOPING OFFSET PRINTING PLATES, and U.S. Pat. No. 3,916,426, issued Oct. 28, 1975, to Delos E. Bown, also for an APPARATUS FOR DEVELOPING OFFSET PRINTING PLATES. Both of these patents are assigned to the assignee of the present application. The disclosure of each of these patents is hereby incorporated herein by reference.
In the machine disclosed in U.S. Pat. No. 3,732,808, a plate to be developed is fed horizontally between two rollers which feed it into a first developing station, where it is sprayed with a developer solution. From there it proceeds between two brush rollers, which feed it into a second developer chamber where it is again sprayed. After leaving the second developer chamber, it is squeegeed by passing between dryer rollers, which feed it out from the machine.
In the machine disclosed in U.S. Pat. No. 3,916,426, a plate is fed by means of rollers into a developing station where it is spread with developer. It is then fed sequentially through two pairs of scrubber brush rollers and then fed into a rinsing station, where it is sprayed with water or another suitable rinsing solution. After this it is fed by an additional set of rollers into a gumming station, where it is coated with a gumming solution to protect the non-printing portions of the plate during storage. From the gumming station, it is fed out through a drying station, where it is dried by means of warm air. It is then ejected from the machine by means of a delivery station.
Conventional developing apparatus, such as that described above, suffers from a number of problems. One of the most severe of these is that plates being developed are often scratched by contact with the rolls of the developing, or soaking, chamber. These walls, or soaker plates, are conventionally made of stainless steel, which can easily scratch the delicate surface of a lithographic or similar plate. Soaker plates also frequently adhere to a lithographic plate passing between them. This problem is especially severe with thin lithographic plates such as those of 0.004 and 0.006 gauge size.
Other problems also frequently occur in conventional developing machines. For example, it is often necessary to clean GAN (grain anodized) plates developed by means of such a machine. Other types of plates, especially WIN (smooth) and DSN (double sides smooth) plates, frequently jam while moving through the machine.